System integration of a steam reformer and gas turbine

ABSTRACT

A novel process and apparatus for power generation from biomass and other carbonaceous feedstocks are provided. The process integrates a pulse combustor steam reformer with a gas turbine to generate electricity such that (i) efficiency is higher than those of conventional and current advanced power systems, (ii) emissions are lower than those proposed in the new environmental regulations, and (iii) performance is comparable to that of combined cycle, even though a bottoming cycle is not included here. The pulse combustor steam reformer generates a hydrogen-rich, medium-Btu fuel gas that is fired in a gas turbine to generate electricity. The apparatus may be configured to produce only power or combined heat and power.

RELATED APPLICATIONS

[0001] The present application is based upon a provisional applicationfiled on Aug. 19, 1999 having Ser. No. 60/149,870.

FIELD OF THE INVENTION

[0002] The present invention relates to a thermomechanochemical processand apparatus for efficient, clean, modular, cost-effective, green andclimate-change neutral power or combined heat and power generation frombiomass. Other carbonaceous feedstocks can be used as well.

BACKGROUND OF THE INVENTION

[0003] Many different options are available for power generation. Thefuel can be combusted, gasified, pyrolyzed, bioprocessed or liquefiedand utilized in engines, steam power plants (boiler, steam turbine,etc.), gas turbines, gas and steam power plants,. and fuel cells. Amongthese, the most efficient and environmentally superior route forelectric power generation is, of course, fuel cells. For the small-scalepower (10 KW_(e) to 5 MW_(e)) sector, combined-cycle units are generallynot applicable due to low efficiency and high cost. Such traditionalsteam power plants are generally less than 20% efficient. Engines aremore efficient (20 to 40%), but are typically fired with diesel ornatural gas. A more viable alternative to fuel cell technology in thenear-term is a biopower system based on a gas turbine.

[0004] However, many conventional power plants based on biomasscombustion have experienced operational difficulties, especially whenfiring non-wood biomass fuels. These problems resulted from thedeposition of mineral matter on heat exchange surfaces (boiler tubes,superheaters and water walls) or from the agglomeration of ash in thefluidized bed. Gasification of biomass, in contrast, renders it possibleto avoid these problems, minimize emissions and integrate with the fuelcell.

[0005] Currently, there exists many types of gasifiers, such as highpressure, low pressure, partial oxidation, autothermal, indirectlyheated, oxygen/air/steam-blown, fixed/fluidized bed or entrained flowgasifiers. Each system has its advantages. For example, in directgasification, partial oxidation or autothermal reactions are employedthat yield an undesirable low-Btu fuel gas that requires oxygen input.The production of a low-Btu fuel gas is due to the fact that bothexothermic and endothermic reactions take place in situ in the case ofdirect gasification, and the products of exothermic reactions dilute theproduct gases to be combusted for gas turbine power generation.

[0006] In view of the above, currently, a need exists for a newgasification process that is better suited for power generationapplications.

SUMMARY OF THE INVENTION

[0007] In accordance with the present invention, a process for producingelectricity from carbonaceous materials is disclosed. The carbonaceousmaterials can be, for instance, coal, pulp and paper waste, woodproducts such as wood chips or sawdust, municipal waste, industrialwaste, sewage, food waste, plant matter, rice straw, and animal waste.

[0008] The process includes providing a fluidized bed containing aparticulate material and a fluidizing medium. The fluidizing medium issteam. The particulate material can have a particle size less than about500 microns and can include sand, alumina, magnesium oxide, and thelike.

[0009] Any suitable combustion device can be used to indirectly heat thefluidized bed. In one embodiment, a pulse combustion device combusts afuel source to form a pulse combustion stream. The pulse combustionstream indirectly heats the fluidized bed. As used herein, indirectlyheating the bed means that the pulse combustion stream does not contactthe contents of the bed.

[0010] A carbonaceous material is fed to the fluidized bed. Thefluidized bed is maintained at a temperature sufficient for thecarbonaceous materials to endothermically react with the steam to form aproduct gas stream. The product gas stream can contain, for instance,lower molecular weight hydrocarbons. The product gas stream is then fedto a gas turbine. The gas turbine combusts the product gas stream inorder to rotate a turbine and generate electricity. In one embodiment,the product gas stream can be compressed by a gas compressor and mixedwith air prior to being combusted in the gas turbine.

[0011] The temperature in the fluidized bed can be from about 900degrees F. to about 1800 degrees F., and particularly from about 1100degrees F. to about 1600 degrees F. The carbonaceous materials canremain in the bed for a time from about ½ hour to about 15 hours, andparticularly from about 2 hours to about 10 hours. For mostapplications, the weight ratio between steam and the carbonaceousmaterials can be from about 0.75:1 to about 3:1.

[0012] In order to conserve energy, in one embodiment, a portion of theproduct gas stream is fed to a heat exchanger that heats steam which isfed to the fluidized bed. Steam can also be generated or heated usingthe flue gas from the pulse combustion device.

[0013] The flue gas of the pulse combustion device can also be used toheat air being fed to the gas turbine and can be used to heat orgenerate steam fed to a dryer for drying the carbonaceous materialsprior to being fed to the fluidized bed.

[0014] In order to clean the product gas stream prior to being combustedin the gas turbine, the product gas stream can be fed through a cyclonefor removing particulate material and can be fed to a scrubber forremoving hydrogen sulphide or other undesirable constituents.

[0015] In one embodiment of the present invention, the process isparticularly well suited to processing rice straw. When processing ricestraw, silica separates from the straw in the fluidized bed which can becollected and recovered. The silica can then be used to formsemiconductor wafers and other useful articles.

[0016] In an alternative embodiment, the process of the presentinvention is well suited to treating animal waste. In this embodiment,the fluidized bed should be at a temperature of at least 1400 degrees F.When processing animal waste, fertilizer components, such as nitrogen,phosphorous and potassium can be recovered during the process.Specifically, phosphorous and potassium can be recovered from aparticulate removal device that is placed in communication with theproduct gas stream exiting the fluidized bed. Nitrogen, on the otherhand, can be recovered as ammonia from the product gas stream.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A full and enabling disclosure of the present invention,including the best mode thereof, to one skilled in the art, is set forthmore particularly in the remainder of the specification includingreference to the accompanying figures in which:

[0018]FIG. 1 is a schematic diagram of one embodiment of a process madein accordance with the present invention;

[0019]FIG. 2 is a block-flow diagram of the process of the presentinvention;

[0020]FIG. 3 is another block-flow diagram of a process made inaccordance with the present invention;

[0021]FIG. 4 is a plan view of a pulse combustion device that may beused in the process of the present invention;

[0022]FIG. 5 is a schematic diagram of an alternative embodiment of aprocess made in accordance with the present invention; and

[0023]FIG. 6 is still another alternative embodiment of a schematicdiagram of a process made in accordance with the present invention.

[0024] Repeat use of reference characters in the present specificationand drawings is intended to represent same or analogous features orelements of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] It is to be understood by one of ordinary skill in the art thatthe present discussion is a description of exemplary embodiments only,and is not intended as limiting the broader aspects of the presentinvention, which broader aspects are embodied in the exemplaryconstructions.

[0026] The present invention is directed to a gasification process thatintegrates a steam reformer with a gas turbine. In particular, thepresent invention is directed to a novel process and apparatus thatintegrates a pulse combustor with a steam reformer and gas turbine togenerate electricity, i.e. a thermomechanochemical system (TMCS).

[0027] Although the use of pulse combustors is relatively well-known inthe art, as indicated for example by U.S. Pat. Nos. 5,059,404,5,133,297, 5,255,634, 5,211,704, 5,205,728, 5,366,371, 5,197,399,5,353,721, 5,638,609, and 5,637,192 which are herein incorporated byreference, it is believed that the novel pulse combustor steam-reformingprocess of the present invention is better suited for power generationapplications.

[0028] The product gases of a process of the present invention aretypically hydrogen-rich, medium-Btu gases (does not need oxygen input)generated through endothermic reactions in a reducing environment. Theheat of reaction is supplied indirectly by the resonance tubes of one ormore modular pulsating burners. This maximizes the calorific value ofthe reformate gas used in the gas turbine and, hence, maximizes theelectrical conversion efficiency of the power plant.

[0029] A system of the present invention also overcomes the limitationsof prior oxygen-blown partial oxidation and two-stage circulating solidsgasification systems. In contrast to these systems, a system of thepresent invention provides that biomass (waste or cultivated) feedstockbe fed to a single fluidized bed vessel and reacted with steam togenerate a hydrogen-rich product gas.

[0030] The use of a single fluidized bed offers an ideal environment foreffecting the endothermic steam-reforming reaction with the heatsupplied indirectly through heat transfer surfaces that are formed fromthe resonant section of a pulse combustor immersed within the fluid bed.These pulsations translate into improved heat transfer rates (as much as3 to 5 times) through the fire tubes and into the fluid bed.

[0031] Using a system of the present invention, a synthesis qualityproduct gas can be generated from a wide spectrum of feedstocksincluding biomass, coals, municipal waste, refuse-derived fuel (RDF),industrial sludges, and spent liquor from the pulp and paper industry,without the use of air or oxygen.

[0032] Moreover, the product gas is free of both diluent nitrogen andcombustion-generated CO₂. The complete reforming process is accomplishedusing only a single vessel, and no circulation of hot solids is needed.The combustion process utilizing clean product gas eliminates the needfor flue gas treatment from the combustors.

[0033] According to the present invention, one embodiment of thethermomechanochemical system (see FIGS. 2 and 3) includes a fluidizedbed reactor that is indirectly heated by multiple resonance tubes of oneor more pulse combustion modules. Feedstock such as biomass, coal,sludge or spent liquor is fed to the reactor which is fluidized withsuperheated steam from a waste heat recovery boiler. The organicmaterial injected into the bed undergoes a rapid sequence ofvaporization and pyrolysis reactions. Higher hydrocarbons released amongthe pyrolysis products are steam cracked and partially reformed toproduce low molecular weight species. Residual char retained in the bedis more slowly gasified by reaction with steam.

[0034] In one embodiment, the product gases are routed through a cycloneto remove bulk of the entrained particulate matter and are quenched andscrubbed in a venturi scrubber. A portion of the medium-Btu productgases are supplied to the pulse combustion modules and combustion ofthese gases provides the heat necessary for the indirect gasificationprocess.

[0035] Accordingly, a system of the present invention integrates athermochemical reaction subsystem with the gas turbine subsystem togenerate electricity from biomass. The thermochemical reaction subsystemtypically includes a pulse combustor, steam reformer, gas cleanup train,steam superheater, and heat recovery steam generator (HRSG). Part of theproduct gas generated by the steam reformer can be used in the pulseheaters and the remainder can be sent to the gas turbine subsystem forpower generation. The fuel gas generated by the steam reformer generallyundergoes one or more gas cleanup steps in order to meet the fuel gascleanliness requirements of the gas turbine and comply with theenvironmental regulations. The gas turbine subsystem typically includesan air compressor, turbine, and generator.

[0036] An integrated, modular and cost-effective thermomechanochemicalsystem of the system can offer the ensuing benefits when used forbiopower generation:

[0037] enable the electrification of remote rural areas in the U.S. andin the rest of the world and power rural development;

[0038] enhance the utilization of renewable energy and thereby refrainfrom aggravating the global climate change;

[0039] provide a “green” technology for markets which have non-fossilmandates;

[0040] cater to power demand, especially in local areas of developingcountries which lack premium fuel and have limited biomass supply due toshort economical transportation radius;

[0041] aid the disposal of agricultural and livestock wastes andresidues in an environmentally non-intrusive or minimally intrusivemanner;

[0042] facilitate the cleanup of areas with radioactive/chemicalcontamination, meet electrical demand and foster economic growth bygainfully employing phytoremediation and thermomechanochemicalconversion;

[0043] motivate and ease the development of a companion system capableof operating on logistic middle distillate fuels for defenseapplications including remote radar and communication stations andtactical mobile ground support sites; and

[0044] significantly lower life-cycle maintenance requirements due tofewer moving parts.

[0045] Several emerging biomass power generation technologies are underdevelopment and marching towards commercialization. These includeIntegrated Gasification Combined Cycle (IGCC) power systems for biomassand black liquor and Stirling engine based power systems. The formersystems are typically large (>50 MWe) while the latter systems aregenerally small (<10 KW_(e)). To enable fair comparisons of theperformance of the IGCC systems with the performance of the proposedsystem, the analysis for the feedstock (wood) was selected to correspondto those used by the referenced investigators. The analysis for wood ispresented in Table 1. These analyses were used in the computersimulations performed for system integration. TABLE 1 BIOMASS ANALYSISWisconsin Maple - Craig and Mann, NREL Ultimate Analysis Weight %, DryCarbon 49.54 Hydrogen 6.11 Nitrogen 0.10 Sulfur 0.02 Chlorine 0.00 Ash0.50 Oxygen 43.73 HHV, Btu/lb, Dry 8,476 Moisture, %, as received 38

[0046] In one embodiment of the present invention, thethermomechanochemical system typically includes the followingsubsystems:

[0047] a biomass handling and feeding subsystem,

[0048] a pulse combustor steam reformer,

[0049] a steam superheater,

[0050] a fuel gas heat recovery steam generator (e.g. HRSG #1),

[0051] a fuel gas cleanup train that can contain, for example, aVenturi/gas cooler or H₂S absorber or ammonia absorber

[0052] a fuel gas compressor,

[0053] heat exchangers (e.g. Heat Exchangers I and II) and a heatrecovery steam generator (e.g. HRSG #2),

[0054] a bed solids handling and storage subsystem, and

[0055] a gas turbine power generation subsystem

[0056] A biomass handling and feeding subsystem of the present inventioncan incorporate storage, preparation, drying and feeding steps. If thebiomass feedstock is in bulk form, it may need to be shredded or choppedto not exceed 2 inches in all 3 dimensions. Also, if necessary, it canbe dried.

[0057] A steam reformer of the present invention is generally a bubblingbed fluidized with superheated steam. Preferably, the steady-state bedmaintains a mean particle size of 250 to 350 microns and is comprisedprimarily of inert material, such as sand or alumina, and some residualcarbon. Superheated fluidization steam can be supplied to thedistribution headers and bubble caps with sufficient pressure drop tomaintain uniform fluidization across the cross-section of the vessel.

[0058] In addition, resonance tubes (or heat exchanger tubes) of acombustion device such as a pulsed heater module of the presentinvention typically serve as efficient sources of heat supply to supportthe endothermic steam-reforming reaction of the biomass. The resonancetubes can be mounted perpendicular to the fluidization steam flow toenhance the heat transfer between the resonance tube walls and thefluid-bed particles.

[0059] In general, utilization of the pulsed heater can decrease therequired surface area for heat transfer and reduce the size and capitalcost of the reformer.

[0060] Referring to FIG. 4, one embodiment of a pulse combustion devicegenerally 12 is shown. Pulse combustion device 12 includes a combustionchamber 18 in communication with a resonance tube 20. Combustion chamber18 can be connected to a single resonance tube as shown or a pluralityof parallel tubes having inlets in separate communication with the pulsecombustion chamber. Fuel and air are fed to combustion chamber 18 via afuel line 22 and an air plenum 24. Pulse combustion device 12 can burneither a gaseous, a liquid or a solid fuel.

[0061] In order to regulate the amount of fuel and air fed to combustionchamber 18, pulse combustion device 12 can include at least one valve26. Valve 26 is preferably an aerodynamic valve, although a mechanicalvalve or the like may also be employed.

[0062] During operation of the pulse combustion device 12, anappropriate fuel and air mixture passes through valve 26 into combustionchamber 18 and is detonated. During start up, an auxillary firing devicesuch as a spark plug or pilot burner is provided. Explosion of the fuelmixture causes a sudden increase in volume and evolution of combustionproducts which pressurizes the combustion chamber. As the hot gasexpands, preferential flow in the direction of resonance tube 20 isachieved with significant momentum. A vacuum is then created incombustion chamber 18 due to the inertia of the gases within resonancetube 20. Only a small fraction of exhaust gases are then permitted toreturn to the combustion chamber, with the balance of the gas exitingthe resonance tube. Because the pressure of combustion chamber 18 isthen below atmospheric pressure, further air-fuel mixture is drawn intothe combustion chamber 18 and auto-ignition takes place. Again, valve 26thereafter constrains reverse flow, and the cycle begins anew. Once thefirst cycle is initiated, operation is thereafter self-sustaining.

[0063] Pulse combustion devices as described above regulate there ownstoichiometry within their ranges of firing without the need forextensive controls to regulate the fuel feed to combustion air mass flowrate ratio. As the fuel feed rate is increased, the strength of thepressure pulsations in the combustion chamber increases, which in turnincreases the amount of air aspirated by the aerodynamic valve, thusallowing the combustion device to automatically maintain a substantiallyconstant stoichiometry over its desired firing range.

[0064] Pulse combustion device 12 produces a pulsating flow ofcombustion products and an acoustic pressure wave. In one embodiment,the pulse combustion device produces pressure oscillations orfluctuations in the range of from about 1 psi to about 40 psi andparticularly from about 1 psi to about 25 psi peak to peak. Thesefluctuations are substantially sinusoidal. These pressure fluctuationlevels are on the order of a sound pressure range of from about 161 dBto about 194 dB and particularly between about 161 dB and about 190 dB.Generally, pulse combustion device 12 can have an acoustic pressure wavefrequency of from about 50 to about 500 Hz and particularly betweenabout 50 Hz to about 200 Hz. Generally, the temperature of thecombustion products exiting the resonance tube 20 in this applicationwill range from about 1200 degrees F. to about 2000 degrees F.

[0065] The biomass used in the present invention can be wet or dried. Ifthe biomass is wet, it can be dried in an indirect dryer and injectedinto the reformer.

[0066] A steam reformer subsystem of the present invention can alsoinclude a superheater to preheat the fluidization steam before it entersthe reformer. In one embodiment, the superheater employs a portion ofthe sensible heat in the fuel gas stream to superheat the steam. Thisreduces the heat load in the reactor, thereby reducing the number ofheater modules required for a specified biomass through put. Accordingto the present invention, solids separation and return can beaccomplished in the steam reformer subsystem by convention solidseparation devices, such as high efficiency, low maintenance cyclones.The designs employed for these components may be identical to those thatare used in catalytic crackers used for years by the refinery industry.A cyclone can efficiently capture small particles and return them to thebed for inventory control and additional reaction.

[0067] Upon exiting a particulate cyclone, the product gas can also bepartially recirculated to the bed through a steam eductor, in oneembodiment, while the bulk of the product gas is processed through thesteam superheater and a heat recovery steam generator (shown as HRSG #1in FIG. 1). The heat absorbed by the water cooling of the pulsed-heatertube sheet also contributes to the steam produced in the HRSG #1. In oneembodiment, steam from HSRG #1 can also supplement steam generated froma waste heat boiler (shown as HRSG #2 in FIG. 1).

[0068] In accordance with the present invention, a portion of the cleanproduct gas can also be recycled for firing in the pulsed heaters. Inone embodiment, the flue gas leaving the pulsed heaters passes throughtwo gas-to-gas heat exchangers (Heat Exchangers I and II), and then tothe boiler (HRSG #2). HRSG #2 functions as a steam generator and as aneconomizer. HRSG#2 can generate medium pressure steam (such as about 330psig) for biomass drying and high pressure steam for superheating.Typically, the superheated steam is used primarily for fluid bedfluidization. Any excess steam can be sent to the gas turbine combustorfor injection into the gas turbine to boost power output.

[0069] The present invention also generally requires the use of a gascleanup system, which functions to remove entrained particulate matter,H₂S and ammonia, if necessary, from the product gas. In one embodiment,the gas exiting HRSG #1 is quenched, saturated with water and scrubbedof particulate matter when contacted with recirculated fluid in ahigh-energy venturi. A condensate bleed stream is discharged from theplant. The gas is then further cooled by countercurrent contact withrecirculated liquid in a packed tower. The-recirculated liquid is cooledin a non-contact heat exchanger. A bleed stream is also discharged fromthe plant. Final scrubbing may be performed, if needed, in acountercurrent absorber with caustic or other absorbent to remove H₂Sand/or ammonia from the product gas. The resulting solution may befurther processed to recover the chemicals.

[0070] In general, a major portion of the fuel gas generated by thethermochemical reaction subsystem can be compressed to a pressureslightly greater than the turbine inlet pressure and thereafter suppliedto the gas turbine combustor. In one embodiment, air is also typicallycompressed and preheated in Heat Exchanger II and supplied to the gasturbine combustor as an oxidant.

[0071] The products of combustion, along with any excess steam from thesuperheater, can then be injected into the gas turbine coupled with agenerator to produce electricity. In one embodiment, a small portion ofthe flue gas leaving the gas turbine is preheated in Heat-Exchanger I toa temperature near fluid bed temperature and used as vitiated air in thepulsed heaters.

[0072] The fuel gas generally combusts in the pulse heaters and suppliesthe heat for the endothermic reactions in the fluid bed. In oneembodiment, the flue gas exiting the pulse heaters transfer heat to bevitiated air in Heat Exchanger I and then facilitates final preheat ofthe compressed air in Heat Exchanger II. The flue gas from the gasturbine provides for the initial preheating of the compressed air inHeat Exchanger II.

[0073] A system of the present invention as described above maximizesthe energy input to the gas turbine cycle, minimizes fuel gas use forpulse heating and avoids the need for a bottoming steam cycle. Computeranalysis indicates the net electrical efficiency to be on the order ofat least 20 percent on LHV basis for a 1 to 5 MW_(e) biopower system.This is a significant improvement in energy conversion efficiency inaddition to the minimal environmental impact as compared to the state ofthe art in small-scale biomass power systems.

[0074] An example of design parameters for one embodiment of a steamreformer system of the present invention are furnished in Table 2 forreference. Because there is no built-in catalyst as in black liquorapplication, the bed temperature typically should be higher (˜1,475° F.)for wood to achieve high carbon conversion. Experimental data from theProcess Development Unit indicate a total carbon conversion of about 98percent in the 1,450° F. to 1,500° F. temperature range.

[0075] Some biomass feedstocks, such as switch grass, contain a higherproportion of alkali (sodium and potassium), which may lead to theformation of eutectics or low-melting compounds and bed agglomerationand defluidization. To minimize this, the bed material can comprisealumina or magnesium oxide and not sand (to minimize the formation ofsilicates) for those feedstocks, allowing the fluidization velocity tobe higher (˜2 ft/s).

[0076] Design calculations for the parameters of the embodiment depictedin Table 2 indicated that the nominal wood throughput was 3.35 drytons/h for a two 253-tube pulse heater configuration. TABLE 2 NOMINALDESIGN PARAMETERS Steam Reformer Feedstock Wood Fluid Bed Temperature, °F. 1,475 Freeboard Pressure, psig 7.5 Feed Rate, dry TPH 3.35 to 3.5 Fluidization Velocity, 1.5 to 2   ft/s Fluidization Medium Steam DenseFluid Bed Flow 62 Area, ft² Number of Pulse Heater 2 Modules Number ofResonance 253 Tubes/Heater

[0077] The composition of the fuel gas exiting the gas cleanup train ofthe embodiment depicted in Table 2 is shown in Table 3: TABLE 3Component (Volume %) H₂ 49.95 CO 22.70 CO₂ 14.93 H₂O 9.68 N₂ 0.00 CH₄2.29 C₂H₄ 0.30 C₂H₆ 0.07 C₃H₆ 0.02 C₃H₈ 0.00 NH₃ 0.07 H₂S 0.01 HHV,Btu/scf 265

[0078] The net power output was estimated to be about 4.7 MW_(e) and thenet electrical efficiency is about 30.2% on LHV basis.

[0079] The emissions projected for one embodiment of athermomechanochemical system of the present invention are listed inTable 4. The emissions are listed on the basis of lb/MMBtu to enablecomparison with the proposed new environmental regulations (one-tenth ofNew Source Performance Standards or {fraction (1/10)} NSPS). Due tosteam reforming and fuel gas cleanup, the emissions were all very lowand are significantly lower than the proposed regulations. TABLE 4PROJECTED EMISSIONS Lb/MMBtu Wood 1/10 NSPS CO 0.03 — SO₂ 0.04 0.12NO_(x) 0.05 0.06 Particulates <0.0001 0.003

[0080] Referring to FIG. 1, one embodiment of a system made inaccordance with the present invention is illustrated. As shown, thesystem includes a biomass feed 30 which, if necessary, can be designedto shred or chop the materials entering the system. The system can alsoinclude a dryer 32 as shown for removing moisture.

[0081] Once prepared, the biomass materials are then fed to a fluidizedbed 34 which is heated by one or more pulse combustion devices 12. Asshown, in this embodiment, the fluidized bed 34 is heated by three pulsecombustion devices 12 which each include multiple resonance tubes. Thefluidized bed 34 is fluidized with superheated steam and containsparticulate material, such as alumina, sand, a metal oxide such asmagnesium oxide, or any other suitable material. In the fluidized bed34, the biomass materials undergo endothermic reactions and are reformedinto a product gas stream containing lower molecular weighthydrocarbons.

[0082] Upon exiting the fluidized bed 34, the product gas stream is fedto a cyclone 36 for removing particulate matter and then ultimately fedto a gas turbine generally 38. Specifically, the product gas stream isfirst compressed by a gas compressor 42 and fed to a combustor 40. Airis fed to an air compressor 44 and combined with the product gas streamin the combustor 40. The energy from combustion is then used to rotate aturbine 46 which is in communication with a generator 48. Generator 48then produces electricity.

[0083] Prior to being fed to the gas turbine 38, however, the productgas stream can be used to generate steam for use in the fluidized bed ina heat recovery steam generator 50. The steam that is generated in thesteam generator 50 is also super heated by the product gas stream in aheat exchanger 51.

[0084] From the steam generator 50, the product gas stream is fed to aventuri/gas cooler 52 and cooled.

[0085] Besides the product gas stream, the flue gas stream exiting thepulse combustion devices 12 are also further used in the system. Asshown, the flue gas stream from the pulse combustion devices is fed to afirst heat exchanger 54 and to a second heat exchanger 56. Heatexchanger 54 is used to heat a portion of the combustion productsexiting the gas turbine 38. Heat exchanger 56, on the other hand, isused to preheat air entering the combustor 40.

[0086] From the heat exchanger 56, the flue gas stream of the pulsecombustion devices is then fed to a second heat recovery steam generator58. Steam generator 58 generates steam and acts as an economizer.Particularly, as shown, steam exiting the steam generator 58 can be fedto the dryer 32 for drying the biomass materials. Steam from the steamgenerator 58 is also fed to the superheater 51 for use in the fluidizedbed 34.

[0087] Upon exiting the steam generator 58, the flue gas is then fed toa stack and released to the environment if desired.

[0088] As shown, the fluidized bed solids can be periodically collectedif desired. Depending upon the biomass feed materials, the bed solidsmay contain useful components that can be collected and reused.

EXAMPLE 1

[0089] Early system tests were performed using three different biomassfeeds: pistachio shells, wood chips, and rice hulls; two differentsludge waste products from a recycle paper mill; and a Kraft mill sludge(the two sludge wastes differed primarily in their plastic content);Refuse Derived Fuel (RDF); and dried Municipal Sludge Wastewater (MSW).The waste paper sludge was obtained from a mill located in NorthernCalifornia. The sludge fraction was composed of short fiber and plasticreject material that is recovered from a clarifier. These sludge wasteswere representative of high moisture waste materials that are generatedin similar mills located throughout the United States. Table 5summarizes the operating conditions for the various test runs in thebench-scale unit. Temperatures were varied over the range ofapproximately 1215° F. to 1450° F. Steam-to-biomass ratios varied fromapproximately 0.75 to 2.6. Test run durations typically ranged from 4 to10 hours. No process operating problems were encountered for any of theruns, including those with rice hulls that have a high ash content andlow ash fusion point. TABLE 5 OPERATING AND PROCESS CONDITIONS FORBIOMASS WASTE TEST RUNS Average Steam Feed Steam To Total Temp Rate RateBiomass Feed Feedstock (° F.) (lb/h) (lb/h) (lb/lb) (lbs) PistachioShells 1,317 35.5 26.0 0.7 337.0 Pistachio Shells 1,216 30.6 31.5 1.0115.3 Wood Chips 1,286 22.9 31.4 1.4 205.7 Rice Hulls 1,326 30.8 26.00.8 185.5 Recycle Paper Mill Sludge 1,250 17.6 36.5 2.1 118.8 Kraft MillSludge Waste 1,250 17.6 36.5 2.1 299.6 RDF (sand bed) 1,450 11.0 29.02.6 66.0

[0090] The resultant gas compositions from the various biomass wastefeedstocks are summarized in Table 6. The methane content appears to berelatively constant (5 to 12%) over the range of feeds and processingconditions tested. Higher hydrocarbons show a decreasing trend withincreasing temperature and a concomitant increase in hydrogen yields.The ratio between carbon monoxide and carbon dioxide appears relativelyconstant. The dry gas heating value typically ranged from 370 to 448Btu/scf. TABLE 6 GAS COMPOSITIONS MD PRODUCT YIELDS FOR BIOMASS AND MILLSLUDGE TESTS CONDUCTED IN PULSE-ENHANCED INDIRECT STEAM REFORMER RecycleRecycled Mill Waste Kraft RDF MSW Composition Pistachio Pistachio WoodRice Fiber Paper Mill Sand Sand (Vol. %) Shells Shells Chips Hulls WasteW/Plastics Sludge Bed Bed H₂ 37.86 35.04 48.11 42.83 38.86 50.50 52.9445.54 55.21 CO 18.84 23.43 22.91 19.67 23.34 19.26 11.77 25.26 28.10 CO₂28.73 25.20 20.18 24.40 23.27 20.10 21.94 14.51 5.95 CH₄ 10.65 11.318.32 11.56 8.31 8.42 8.95 8.30 5.00 C₂ 3.92 5.02 0.48 1.54 6.40 1.723.00 6.38 5.74 Total 100.00 100.00 100.00 100.00 100.18 100.00 98.6099.99 100.00 HHV 370 406 329 367 412 364 372 418 374 (Btu/scf) TEMP.(°F.) 1317 1216 1286 1326 1250 1326 1250 1450 1410

EXAMPLE 2

[0091] In another project used to evaluate the low NO_(x) potential ofnatural gas-fired pulse combustors, burners of the present inventionwere tested in three different configurations: a pulse burner (0.76 to5.58 million Btu/hr firing rate range) retrofitted to a Cleaver-Brooksboiler and two versions of a pulse combustor from 2 to 9 million Btu/hrincluding a 72-tube heater/heat exchanger bundle of the type used in thesteam-reforming process. In all the cases, the NO_(x) emissions measuredwere less than 30 ppm @ 3% O₂. Emissions data from a pilot-scale 72-tubeheater/heat exchanger bundle that had already accumulated more than5,000 hours of operation was measured by several instruments and ispresented in Table 7. TABLE 7 EMISSIONS DATA FROM THE 72-TUBEPILOT-SCALE PULSE HEATER TESTS FLUE GAS CORRECTED FLUE CORRECTED FLUEGAS CORRECTED READINGS AT 3% O2 READINGS AT 3% O2 READINGS AT 3% O2FIRING RATE O2 NOx NOx O2 NOx NOx O2 NOx NOx (Btu/hr) (%) (ppm) (ppm)(%) (ppm) (ppm) (%) (ppm) (ppm) 1.73E + 06 13.9 2 5.1 13.8 6 15.0 13.6 00 1.74E + 06 16.1 1 3.7 16.3 0 0 15.9 0 0 3.39E + 06 13.4 2 4.7 13.6 49.7 — 0 0 3.39E + 06 14.8 1 2.9 16.7 0 0 16.3 0 0 3.39E + 06 16.5 1 4.09.4 11 17.1 — — 5.10E + 06 8.8 17 25.1 8.8 22 32.5 — — 5.10E + 06 11.114 25.1 — — — 8.6 16 23.2

[0092] In one embodiment of the present invention, it has beendiscovered that various advantages are achieved when the biomassmaterial contains rice straw or other feedstocks rich in silica. It hasbeen discovered that the silica in the rice straw or other feed stockcan be recovered as a valuable byproduct.

[0093] Referring to FIG. 5, one embodiment of a system designed toprocess rice straw according to the present invention is shown. Likereference numerals similar to FIG. 1 have been used to identify similarelements. As shown, in this embodiment, the biomass materials 30 containrice straw. If the rice straw is in bulk form, the straw may need to beshredded or chopped to not exceed two inches in length. As shown, therice straw is fed to a fluidized bed in accordance with the presentinvention and converted into a product gas stream which is ultimatelyused to generate electricity via a gas turbine 38.

[0094] As opposed to the embodiment illustrated in FIG. 1, the system inFIG. 5 includes a steam generator 58 in conjunction with a boiler 62.Further, the system illustrated in FIG. 5 includes an absorber 60 forscrubbing the product gas stream and removing unwanted constituents.Boiler 62 is for generating steam that is fed to the superheater 51. Thesystem further includes a de-aerator 64 for removing air from water fedto the steam generator.

[0095] In this embodiment, the bed solids are drained continuously tomaintain bed height. The solids are cooled and stored. The silica in therice straw is anticipated to be in an amorphous form with a compositionof SiO_(x)(X<2) due to the reducing environment in the steam reformer.Therefore, the bed solids are expected to become a valuable byproductfor the manufacture of silicon PV cells, wafers and chips.

[0096] The nominal design parameters for the steam reformer for a ricestraw application are furnished in Table 8 below. TABLE 8 NOMINAL DESIGNPARAMETERS Steam Reformer Feedstock Rice Straw Fluid Bed Temperature, °F. 1,475 Freeboard Pressure, psig 8.0 Fluidization Velocity, 1.6 ft/sFluidization Medium Steam Dense Fluid Bed Flow Area, 62 ft² Number ofPulse Heater 2 Modules Number of Resonance 253 Tubes/Heater

[0097] Table 9 below shows the analysis for rice straw. TABLE 9 ANALYSISOF RICE STRAW Moisture, as received wt % 8.67 Ultimate Analysis (drybasis) Wt % Carbon 39.6 Hydrogen 4.6 Nitrogen 0.7 Sulfur 0.11 Chlorine0.26 Ash 18.3 Oxygen 36.43 HHV, Btu/lb 6,492 Ash Analysis wt % ash Si0₂72.2 Al₂0₃ 0.1 Na₂0 0.4 K₂0 16.6

[0098] The estimated composition of the flue gas after the gas clean uptrain is shown in Table 10. TABLE 10 COMPOSITION OF FUEL GAS AFTER GASCLEANUP Component (Volume %) H₂ 49.56 CO 23.20 CO₂ 16.36 H₂O 7.65 N₂0.00 CH₄ 2.40 C₂H₄ 0.31 C₂H₆ 0.07 C₃H₆ 0.02 C₃H₈ 0.00 NH₃ 0236 H₂S 0.00HHV, Btu/scf 267

[0099] The emissions projected for the integrated system are listed inTable 11 below. TABLE 11 PERFORMANCE SUMMARY 1 MW_(e) 5 MW_(e) NOMINALSIZE Rice Straw Processing Rate, 33.0 112.1 ton/day dry Gas Turbine NetPower, MW_(e) 1.20 4.87 Plant Power Consumption, MW_(e) 0.07 0.20 NetElectrical Efficiency - % HHV Basis 21.6 26.3 - % LHV Basis 23.1 28.1Byproduct Ash Drain Rate, lb/h 524 1,782 Silicon Content in Ash, % 31 31EMISSIONS No_(x), lb/MBtu 0.11 0.14 SSO₂, lb/MBtu 0.02 0.02Participates, lb/MBtu <0.0001 <0.0001 CO, lb/MBtu 0.03 0.03 VOC, lb/MBtu0.003 0.003

[0100] Besides rice straw, in another embodiment, the process of thepresent invention is used to process farm animal waste. In particular,the process of the present invention can be used to process farm animalwaste in a manner that not only produces steam, but also producesnutrients, such as potassium, phosphorous, and nitrogen which arerecovered as fertilizer-grade byproducts.

[0101] The intensive production of poultry and livestock (billions ofchickens and millions of cattle and pigs annually in the United States)has increased the generation of manure and aggravated the wasteddisposal problem.

[0102] For instance, a 1000 pound dairy cow excretes about 82 pounds ofmanure per day containing 0.4 pounds of nitrogen, 0.17 pounds ofphosphate and 0.32 pounds of potash and 1000 broilers excreteapproximately 140 pounds of manure each day containing 2.4 pounds ofnitrogen, 1.23 pounds of phosphate and 0.9 pounds of potash. The poultrymanure is typically drier and richer in nutrients in comparison tolivestock manure. Therefore, poultry manure affords greater energy andnutrient recovery per ton and in turn the potential for greatercost-effectiveness. It should be understood, however, that the processof the present invention can be used to process any type of animalwaste.

[0103] It is believed that power plants made according to the presentinvention in the 20 kW to 100 kW size range are best suited forprocessing animal waste. For a superior performance, the steam reformerfluidized bed should operate at about 1500 degrees F.

[0104] It is a vision that systems made according to the presentinvention will permit many modular units to be conveniently located nearanimal farms. Distributed power generation has been shown to enhancegrid reliability by providing many geographically diverse power sourcesregardless of type. In addition, the versatility and fuel flexibility ofthe steam reformer permits continued power generation at affordable ormarket competitive rates by switching feed stocks according toavailability and price.

[0105] A schematic diagram of one embodiment of a system made accordingto the present invention for producing electricity from animal waste isillustrated in FIG. 6. A trial was run similar to the system illustratedin FIG. 6 using chicken waste as the feed material.

[0106] When operating the system, there are four variables of relevanceincluding fluid bed temperature, steam fluidization velocity, gasresidence time, and manure composition. Bed temperature impacts heat andmass transfer and reaction kinetics and in turn influences product gascomposition and yield, carbon conversion and residuals solidscomposition. Steam fluidization velocity affects fluidization quality,fines elutriation, steam to carbon ratio and tendency for agglomeration.Gas residence time depends upon fluidizing velocity, dense bed heightand freeboard height and impacts product gas composition and yield,carbon conversion, residual solids composition and tendency foragglomeration. During testing, fluid bed temperature was the onlyparameter that was varied.

[0107] The following is a short description of the start up andoperation of the reactor. The cooling air to the feeder auger andnitrogen flow to the hopper are started. An initial bed material (17.5pounds of magnesium oxide in this example) is loaded into the reactorthrough the port in the top flange. Initial representative samples ofthis bed material and waste are then taken. At the beginning of a test,the bed is fluidized by utilizing nitrogen (about 50 SCFH). At thattime, the heaters are set to a specified temperature and reactorpreheating begins. The gas preheater temperature is set to 1000 degreesF. When the bed temperature approaches 800 degrees F., theboiler-superheater temperature is set to 1000 degrees F. When thesuperheater temperature reaches about 800 degrees F., fluidization isswitched from nitrogen to superheated steam. The water supply rate tothe boiler-superheater is precisely provided by a high pressure meteringpump. An oxidizer is started during the preheating stage and prior toswitching to super-heated steam. When the reactor reaches the specifiedfinal bed temperature, the chicken waste feed is started at a specificdesign feed rate.

[0108] Table 12 below provides a summary of the operating conditions forthe three tests. TABLE 12 TEST PROGRAM SUMMARY Test Numbers 1 2 3Distributor Plenum Mean F 877 863 1050 Temperature Bed Mean TemperatureF 1106 1296 1504 Freeboard Mean Temperature F 828 1074 1122 DistributorPlenum Pressure psig 4 4 2.5 Freeboard Pressure psig 0 0 0 Water Flowfor Fluidizing Steam ml/min 5.2 4.5 4.3 Fluidizing Nitrogen l/min 2.362.36 0 Feeder Bin Purge Nitrogen l/min 0.57 0.57 0.57 Waste Feed Rateg/min 6.5 5.6 5.0 Superficial Fluidization Velocity ft/s 0.15 0.15 0.14

[0109] It was discovered that the initial bed is all magnesium oxide andwhite in color. The bed samples at the end of the 1100 degrees F. and1300 degrees F. tests were dark indicating leftover carbon. The bedfollowing the 1500 degree test, however, had a few specks of gray andexhibited a slight tan. This suggests excellent carbon conversion at1500 degrees F.

[0110] Complete laboratory analysis of all the samples were made onlyfor the 1500 degrees F. test. Only the initial and final bed sampleswere analyzed for the 1100 degree F. and 1300 degree F. tests. All ofthe chemical analyses were performed by an outside laboratory. Theresults are presented in Tables 13 through 22. Tables 13 through 20correspond to the 1500 degree F. test while Tables 18 and 21 relate tothe 1100 degree F. test and Tables 18 and 22 refer to the 1300 degree F.test. TABLE 13 PRODUCT GAS COMPOSITION AND HHV Vol, % Hydrogen H2 55.29%Oxygen O2 0.00% Nitrogen N2 0.00% Methane CH4 6.16% Carbon Monoxide CO6.12% Carbon Dioxide CO2 28.51% Ethylene C2H4 3.35% Ethane C2H6 0.13%Acetylene C2h2 0.16% Hydrogen Sulfide H2S 0.28% Propylene C3H6 0.00%Propane C3H8 0.00% HHV Btu/dry scf 322.4 Btu/g dry feed 13.1 Btu/lb dryfeed 5.936 Btu/Btu in dry feed 1.2

[0111] TABL 14 ELEMENTAL BALANCE In Out Closure Element g/h g/h % C78.45 66.87 85.2 H 55.30 57.50 104.0% O 410.59 428.37 104.3% N 7.84 3.5144.7% S 1.46 1.37 93.8% K 5.33 2.62 49.1% P 3.54 0.86 24.3% C 2.68 2.4892.7% Ash 88.28 90.28 102.3%

[0112] TABLE 15 CONVERSION AND RELEASE DATA Min Max Carbon conversion98% 99% Sulfur release 84% 89% Chlorine release 91% 98% Nitrogen release41% 92%

[0113] TABL 16 VOC IN THE PRODUCT GAS STREAM VOC Mg/g of dry feedAcetone 0.0067 Acrylonitrile 0.0073 Benzene 0.0555 Toluene 0.0130Xylenes 0.0008 Styrene 0.0048 Naphthalene 0.0242 Acetonitrile 0.0058Thiophene 0.0016 Other 0.0229 Total VOC 0.143 mg/g of dry feed 0.065g/lb of dry feed

[0114] TABL 17 SVOC IN THE PRODUCT GAS STREAM SVOC mg/g of dry feedPhenol 0.0293 Naphthalene 0.9512 Fluorene 0.1353 Acenaphthene 0.3051Phenanthrene 0.2256 Other 1.7539 Total 3.40 mg/g of dry feed 1.54 g/lbof dry feed

[0115] TABLE 18 BED COMPOSITION BEFORE AND AFTER THE TEST Weight, g Test1 Test 2 Test 3 Elements Before After Before After Before After C 054.40 0 4.00 0   0.40 H 0 6.40 0 2.00 0   2.00 O 0 0.00 0 0.00 0   0.00N 0 1.60 0 0.80 0   0.80 S 0 2.72 0 1.28 0   0..20 K 0 24.96 0 12.40 0  0.04 P 0 8.80 0 4.80 0   0.40 Cl 0 9.60 0 2.80 0   0.16 Ash 8000 80478000 8016 8000 8003 (including MgO) TOTAL 8000 8156 8000 8044 8000 8007

[0116] TABL 19 COMPOSITION OF ELUTRIATED SOLIDS g/g dry Elements feed C0.0040 H 0.0002 O 0.0000 N 0.0002 S 0.0003 K 0.0105 P 0.0030 Cl 0.0096Ash 0.3625 Total 0.3903

[0117] TABLE 20 NUTRIENT DISTRIBUTION Gas Catch Bed N min 41%  1%  3%max 92%  2%  7% K min  0%  49%  0% max  0% 100%  0% P min  0%  21%  3%max  0%  87% 13%

[0118] TABL 21 PRODUCT GAS COMPOSITION AND YIELD FOR TEST 1 (1,000° F.)Hydrogen H₂ 47.63% Oxygen O₂ 0.00% Nitrogen N₂ 0.00% Methane CH₄ 4.31%Carbon Monoxide CO 12.68% Carbon Dioxide CO₂ 30.05% Ethylene C₂H₂ 2.33%Ethane C₂H₆ 0.74% Acetylene C₂H₂ 0.00% Hydrogen Sulfide H₂S 1.82%Propylene C₃H₆ 0.43% Propane C₃H₈ 0.00% HHV Btu/dry scf 312 Btu/g dryfeed 9.1 Btu/lb dry feed 4,111 Btu/Btu in dry 0.82 feed

[0119] TABL 22 PRODUCT GAS COMPOSITION AND YIELD FOR TEST 2 (1,300° F.)Hydrogen H₂ 51.90% Oxygen O₂ 0.00% Nitrogen N₂ 0.00% Methane CH₄ 9.48%Carbon Monoxide CO 9.44% Carbon Dioxide CO₂ 25.44% Ethylene C₂H₄ 2.36%Ethane C₂H₆ 0.42% Acetylene C₂H₂ 0.04% Hydrogen Sulfide H₂S 0.69%Propylene C₃H₆ 0.22% Propane H₂ 0.00% HHV O₂ 351 N₂ 18.3 CH₄ 8,315 H₂1.65

[0120] The product gas composition on a dried basis is presented inTable 13. Steam reforming produces a medium-Btu reformate gas rich inhydrogen. The HHV is relatively high at 322 Btu/dscf. Product gas yieldachieved 5,936 Btu/pound dry feed or a gas to dry feed HHV ratio of 1.2.This is greater than 1 due to the supply of endothermic heat of reactionby indirect heat transfer by the pulse combustion devices.

[0121] Closures for the material balances are shown by element in Table14. Good closure was obtained for hydrogen, oxygen, ash, sulphur andchlorine. Closures of carbon, nitrogen, potassium and phosphorous,however, were not as good due to possible sample error.

[0122] Table 15 provides the lower and upper bounds for carbonconversion and the release of sulphur, chlorine, and nitrogen. Thecarbon conversion is high and can be improved by incorporating acyclone, reducing freeboard heat losses and increasing gas residencetime in the reactor. Practically all of the chlorine is released and amajority of the sulphur and nitrogen in the feed are released as well.

[0123] Tables 16 and 17 present a summary of VOC and SVOC speciescollected in the gas condensate. The gas condensates were collected withan EPA method 5 sampling train utilizing ice-water bath impendures.

[0124] The bed composition before and after all the tests are given inTable 18. For test 3, trace quantities of the elements are left in thebed. Very little carbon remains in the bed and the feed is either steamreformed or elutriated. This suggests that a bed drain need not beincorporated and a cyclone catch could be the reject solid stream.

[0125] The composition of the elutriated solids is shown in Table 19.Potassium and phosphorous and other inerts mostly seem to stay in thefines. There is significant amount of chloride in this stream and it isplausible that potassium and chloride combined to form a salt.

[0126] Table 20 indicates the nutrient distribution among the gas,cyclone catch and bed streams at 1500 degrees F. Both upper and lowerlimits are given. The lower limit corresponds to feed rate or “in”species and the upper limit corresponds to overall collection rate or“out” species. Nitrogen mainly reports as NH₃ in the gas phase whilephosphorous and potassium show up predominately in the cyclone catch.

[0127] Tables 21 and 22 present the product gas composition and yielddata for tests 1 and 2 respectively.

[0128] As shown in FIG. 6, the biomass system includes a steam reformercontaining pulse combustion devices 12 and a fluidized bed 34. A productgas stream generated in the fluidized bed is fed to a gas turbine 38.When feeding animal waste to the system, preferably the waste materialdoes not have a dimension exceeding two inches in length. If necessary,the waste material can be shredded or chopped. In this embodiment, adryer has been eliminated from the system for simplicity but can beadded, if necessary.

[0129] The fluidized bed 34 is a bubbling bed fluidized with superheatedsteam. The fluidized bed contains a particulate material having a meanparticle size of from about 100 to about 250 microns. The particulatematerial is primarily an inert material, such as magnesium oxide oralumina.

[0130] Resonance tubes of the pulse combustion devices 12 serve asefficient sources of heat supply to support the endothermicsteam-reforming reaction of the biomass. The resonance tubes of thepulse combustion devices are mounted perpendicular to the fluidizationsteam flow to enhance the heat transfer between the resonance tube wallsand the fluid-bed particles.

[0131] Animal biomass is injected into the fluidized bed 34. Asuperheater 51 is used to preheat the fluidization steam before itenters the fluidized bed 34. The superheater 51 employs a portion of thesensible heat in the fuel gas stream to superheat the steam.

[0132] Solid separation and return is accomplished by a high efficiency,low maintenance cyclone 36. The cyclone 36 efficiently captures smallparticles and returns them to the bed for inventory control andadditional reaction. Upon exiting the cyclone 36, the product gas isprocessed through the steam superheater 51.

[0133] A portion of the clean product gas can be recycled for firing inthe pulse combustion devices. The flue gas leaving the pulse combustiondevices 12 passes through a gas-to-gas heat exchanger 54 then to aboiler 62 and to an air preheater 63. The boiler 62 generates lowpressure steam (55 PSIG). The superheated steam is primarily used forfluid bed fluidization. Excess is sent to the gas turbine combustor forinjection into the gas turbine to boost power output.

[0134] If necessary, the system can include gas clean up devices forremoving hydrogen sulphide and ammonia from the product gas. Followingthe superheater 51, the product gas stream is quenched, saturated withwater and scrubbed of particulate matter when contacted withrecirculated fluid in a high-energy venturi 52. A condensate bleedstream is discharged from the system. The product gas is then furthercooled by countercurrent contact with recirculated liquid in a packedtower. The recirculated liquid is cooled in a non-contact heatexchanger. Two sorbent beds 60 in series are used to capture hydrogensulphide and ammonia.

[0135] A major portion of the product gas generated by the fluidized bed34 is compressed in a gas compressor 42 to slightly greater than turbineinlet pressure and supplied to the gas turbine combustor 40. Air is alsocompressed in an air compressor 44 and preheated in a heat exchanger 56.The air is supplied to the gas turbine combustor 40 as an oxidant. Theproducts of combustion along with the excess steam from the super-heaterare injected into the gas turbine generally 38. A generator 48 coupledto a gas turbine 46 produces electricity.

[0136] Air is heated in the preheater 63 and the heat exchanger 54 tonear fluid bed temperature and used in the pulse combustion devices 12.

[0137] Solids captured in the cyclone 36 are drained continuously. Thesolids are cooled in a cooler 70. The potassium and phosphorous in theanimal biomass is contained predominately in the solids. Therefore, thesolids are a valuable byproduct and can be used as desired.

[0138] Tables 23 and 24 below provide the analysis for poultry litterand summarizes the performance and emissions of the tests conducted.TABLE 23 POULTRY LITTER Ultimate Analysis Weight %, Dry Carbon 37.52Hydrogen 5.13 Nitrogen 3.71 Sulfur 0.50 Chlorine 1.06 Ash 21.34 Oxygen31.82 HHV, Btu/lb, Dry 6,390 Moisture, %, as received 27.43

[0139] TABLE 24 PERFORMANCE SUMMARY NOMINAL SIZE 77 kWe Feed: PoultryLitter, tons per day 3.48 Microturbine net power, kW_(e) 87 Plant PowerConsumption, kW_(e) 10 Net Power Export, kW_(e) 77 Net ElectricalEfficiency % HHV Basis 14.2 % LHV Basis 15.2 By product Ash Drain Rate,lb/h 88 Nutrient Content in Ash, wt % 21 EMISSIONS No_(x), lb/MMBtu 0.06SO₂, lb/MMBtu 0.09 Participates, lb/MMBtu 0.0001 CO, lb/MMBtu 0.04 VOC,lb/MMBtu 0.003

[0140] These and other modifications and variations to the presentinvention may be practiced by those of ordinary skill in the art,without departing from the spirit and scope of the present invention. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention.

What is claimed:
 1. A process for producing electricity fromcarbonaceous materials comprising the steps of: providing a fluidizedbed containing a particulate material and a fluidizing medium, saidfluidizing medium comprising steam; combusting a fuel source in acombustion device to form a combustion stream, said combustion streamindirectly heating said fluidized bed; feeding a carbonaceous materialto said fluidized bed, said fluidized bed being at a temperaturesufficient for said carbonaceous material to endothermically react withsaid steam to form a product gas stream; feeding said product gas streamto a gas turbine, said gas turbine combusting said product gas stream inorder to rotate a turbine and generate electricity, said gas turbineproducing a flue gas stream; feeding at least a portion of said productgas stream or said flue gas stream exiting said gas turbine to saidcombustion device for combustion with said fuel source; and whereinprior to said gas turbine, the product gas stream is fed to a heatexchanger for heating steam fed to said fluidized bed.
 2. A process asdefined in claim 1, wherein said steam to said carbonaceous materialhave a weight ratio of from about 0.75:1 to about 3:1.
 3. A process asdefined in claim 1, wherein said combustion device is a pulse combustiondevice.
 4. A process as defined in claim 1, further comprising the stepof using said combustion stream to preheat an air stream that is fed tosaid combustion device for combusting said fuel source.
 5. A process asdefined in claim 1, wherein after exiting said fluidized bed, saidcombustion products are fed to a steam generator for generating steamfed to said fluidized bed.
 6. A process for producing electricity fromcarbonaceous materials comprising the steps of: providing a fluidizedbed containing a particulate material and a fluidizing medium, saidfluidizing medium comprising steam; combusting a fuel source in acombustion device to form a combustion stream, said combustion streamindirectly heating said fluidized bed; feeding a carbonaceous materialto said fluidized bed, said fluidized bed being at a temperaturesufficient for said carbonaceous material to endothermically react withsaid steam to form a product gas stream; feeding said product gas streamto a gas turbine, said gas turbine combusting said product gas stream inorder to rotate a turbine and generate electricity, said gas turbineproducing a flue gas stream; feeding at least a portion of said productgas stream or said flue gas stream exiting said gas turbine to saidcombustion device for combustion with said fuel source; and whereinafter exiting the fluidized bed, the combustion products are fed to asteam generator for generating steam fed to the gas turbine forincreasing mass flow rates through the gas turbine.
 7. A process asdefined in claim 6, wherein said combustion device is a pulse combustiondevice.
 8. A process as defined in claim 6, further comprising the stepof using said combustion stream to preheat an air stream that is fed tosaid combustion device for combusting said fuel source.
 9. A process asdefined in claim 6, wherein prior to said gas turbine, said product gasstream is fed to a heat exchanger for heating steam fed to saidfluidized bed.
 10. A process for producing electricity from carbonaceousmaterials comprising the steps of: providing a fluidized bed containinga particulate material and a fluidizing medium, said fluidizing mediumcomprising steam; combusting a fuel source in a combustion device toform a combustion stream, said combustion stream indirectly heating saidfluidized bed; feeding a carbonaceous material to said fluidized bed,said fluidized bed being at a temperature sufficient for saidcarbonaceous material to endothermically react with said steam to form aproduct gas stream; feeding said product gas stream to a gas turbine,said gas turbine combusting said product gas stream in order to rotate aturbine and generate electricity, said gas turbine producing a flue gasstream; combining an air stream with the product gas stream prior tocombusting the product gas stream in the gas turbine, the air streambeing preheated by the combustion stream exiting the combustion device;preheating at least a portion of the flue gas stream exiting the gasturbine by the combustion stream exiting the combustion device; andfeeding at least a portion of said flue gas stream to said combustiondevice for combustion with said fuel source.
 11. A process as defined inclaim 10, wherein said carbonaceous material comprises a materialselected from the group consisting of coal, pulp and paper waste, woodproducts, municipal waste, sewage, food waste, plant matter, animalwaste, industrial waste, biomass and mixtures thereof.
 12. A process asdefined in claim 10, wherein said carbonaceous material comprises ricestraw and wherein the process further comprises the step of collectingsilica as a byproduct from said fluidized bed.
 13. A process as definedin claim 10, wherein said carbonaceous material comprises animal wasteand wherein a material selected from the group consisting ofphosphorous, nitrogen and potassium are generated and collected duringthe process.
 14. A process as defined in claim 10, wherein saidfluidized bed is maintained at a temperature of from about 900 degreesF. to about 1800 degrees F.
 15. A process as defined in claim 10,wherein said steam to said carbonaceous material have a weight ratio offrom about 0.75:1 to about 3:1.
 16. A process as defined in claim 10,wherein said combustion device is a pulse combustion device.
 17. Aprocess as defined in claim 10, wherein prior to said gas turbine, saidproduct gas stream is fed to a heat exchanger for heating steam fed tosaid fluidized bed.
 18. A process as defined in claim 10, wherein afterexiting said fluidized bed, said combustion products are fed to a steamgenerator for generating steam fed to said fluidized bed.
 19. A processas defined in claim 10, wherein said product gas stream is fed to acompressor prior to being combusted in said gas turbine, said compressorcompressing said product gas stream to a pressure greater than the inletpressure of said gas turbine.
 20. A process as defined in claim 19,wherein said product gas stream is mixed with the preheated air streamprior to being combusted in said gas turbine.
 21. A process as definedin claim 10, wherein after exiting said fluidized bed, said combustionproducts are fed to a steam generator for generating steam fed to saidgas turbine for increasing mass flow rates through said gas turbine. 22.A process as defined in claim 10, wherein the flue gas exiting the gasturbine is fed to a steam generator for generating steam, said steambeing fed to said gas turbine.
 23. A process as defined in claim 10,wherein the air stream is fed to a compressor and compressed prior tobeing preheated by the combustion stream exiting the combustion device.